Detection of Bovine Coronavirus in Healthy and Diarrheic Dairy Calves

BACKGROUND: BCoV is identified in both healthy and diarrheic calves, complicating its assessment as a primary pathogen. OBJECTIVES: To investigate the detection rates of bovine coronavirus (BCoV) in feces of healthy and diarrheic calves and to describe the usefulness of a pancoronavirus reverse transcriptase (RT) PCR (PanCoV‐RT‐PCR) assay to identify BCoV in samples of diarrheic calves. ANIMALS: Two hundred and eighty‐six calves <21 days. Calves with liquid or semiliquid feces, temperature >39.5°C, and inappetence were considered as cases, and those that had pasty or firm feces and normal physical examination were designated as controls. METHODS: Prospective case–control study. A specific BCoV‐RT‐PCR assay was used to detect BCoV in fecal samples. Association between BCoV and health status was evaluated by exact and random effect logistic regression. Fecal (n = 28) and nasal (n = 8) samples from diarrheic calves were tested for the presence of BCoV by both the PanCoV‐RT‐PCR and a specific BCoV‐RT‐PCR assays. A Kappa coefficient test was used to assess the level of agreement of both assays. RESULTS: BCoV was detected in 55% (157/286) of calves; 46% (66/143), and 64% (91/143) of healthy and diarrheic calves, respectively. Diarrheic calves had higher odds of BCoV presence than healthy calves (OR: 2.16, 95% CI: 1.26 to 3.83, P = 0.004). A good agreement between PanCoV‐RT‐PCR and BCoV‐RT‐PCR to detect BCoV was identified (κ = 0.68, 95% CI: 0.392 to 0.967; P < 0.001). CONCLUSIONS AND CLINICAL IMPORTANCE: BCoV was more likely to be detected in diarrheic than healthy calves. The PanCoV‐RT‐PCR assay can be a useful tool to detect CoV samples from diarrheic calves.